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Silver Solder & Flux Question for 440C Stainless (AMS 5630) on Steel

I have a difficult question. I am attempting to silver solder a 440C Stainless (AMS 5630) “doughnut” ring that is .5” long x .25” wall thickness onto a cast iron shaft. The .25” wall is not consistent and can grow to .45” on one side. The sstainless has been hardened to a Rc63-68 (knowing that I will lose some hardness out of the material). Both piece surfaces were sandblasted with a 1200 grit and have a .002” to .003” clearance fit. The shaft o.d. is .750"

I went to the local welding shop and they recommended a 4% sliver solder and a flux (flux is at my shop). I practiced on test pieces that were both steel (not the stainless) and results were very good. When heating up the test pieces and disassembling, they both retained a silver coating. When I try the stainless onto the steel, the solder does not seem to want to “stick”. It will flow into the joint, but it does not provide any metal bonding. The internet provides a million options. It appears as if the solder and flux that I have are not appropriate for the application.

I am getting the heat to it ~350 -375F. The solder appears to flow and go to the heat, but it just does not want to stick or make bond.

Suggestions for both a Solder and a flux please, part numbers, pricing, where to get the supplies....

Try here : http://www.lucasmilhaupt.com/en-US/products/ I've used their Handy flux for many years and been quite happy with it. It is not sticking to the steel or the stainless or both? As mentioned you may not be hot enough.---Meltedmetal

Thank you for the input. Not sticking to both. I did try hotter with no luck. Because of the shape and physical confines, I am only able to heat the thinner side of the ring (about 130° radial). I will contact the supplier mentioned. If there is other input, I greatly appreciate the help.

I'm guessing your using something like their "clean 'n bright" where I would try something more in the line of their "braze 505" or maybe "braze 450". But your looking at a lot more heat. Maybe sign in over there and peruse their product literature etc. Anyway I'm sure they can give you good advice.---Meltedmetal
P.S. Some Handy and Harman or similar products may be available at your local welding supplier.

You folks are good people....3 steps forward, 1 step back....it could have been 2

I want to thank those here on this forum. I have been on other forums where it is hard to get input.

I contacted lucasmilhaupt. Great company tech rep. I will recommend their products from this point out due to the help he gave me. Here is the answer. The cast is not good to solder due to the carbon content. He did indicate that I could get Nickle or Copper plating and then silver solder and it would work.

In parallel to the above, I am also exploring MIG options. I have what I call "Farm Wire" and some Stainless that I have utilized before. I know the stainless that I have takes some amps (heat) to make it flow good (utilizing tri gas). I thought there was a wire out there that was utilized for body work that had a low melting point. I have welded stainless with both the wires and it appears to be ok (structurally ok for the application also).

Thoughts of trying to MIG a stainless to a cast iron? I guess one test is worth it.

I know I am being vague, apologies, but if you have a recommendation for a MIG wire type/diameter to weld a stainless to cast iron (see previous for the sizes/application), it again, is appreciated.

Thanks for the update. Depending on your application you might also oxy/acetylene bronze. It will certainly stick to the cast iron. It is cast and not ductile? They are different animals to weld. Also is it possible to attach it mechanically? Like threading the stainless and the shaft or attaching a collar and using set screws or a pin?---Meltedmetal

I cant attached mechanically without really backing up the forward progress. I am kicking myself a bit, because I thought I had this plan pretty well laid out. I should have driven the details.

I wanted to avoid the brazing as this is ~1000°F+ and that would surely take any HT that I have in the 440C away. I am not really sure what the MIG will do to my HT, thus the question on a thin low melt wire. I would then look at the Tensile/Sheer to determine if it would meet the application.

I have some 440C samples that I am going to practice MIG with. I will let you all know the results.

Your hardened 440c is very likely to crack if you weld it. The heat treat will be gone in the area you weld as the arc from welding will be in the 2500 degree range.
The filler I think your talking about using is silicon bronze and has a low melting point and is very ductile. If you weld the part and it has a shiny finish you can see where the HT is gone in the HAZ (heat affected zone) beside the weld it will turn different colours, blue indicates around 500 degrees and gold is a little cooler and will not affect the ht.

I have a difficult question. I am attempting to silver solder a 440C Stainless (AMS 5630) “doughnut” ring that is .5” long x .25” wall thickness onto a cast iron shaft. The .25” wall is not consistent and can grow to .45” on one side. The sstainless has been hardened to a Rc63-68 (knowing that I will lose some hardness out of the material). Both piece surfaces were sandblasted with a 1200 grit and have a .002” to .003” clearance fit. The shaft o.d. is .750"

I went to the local welding shop and they recommended a 4% sliver solder and a flux (flux is at my shop). I practiced on test pieces that were both steel (not the stainless) and results were very good. When heating up the test pieces and disassembling, they both retained a silver coating. When I try the stainless onto the steel, the solder does not seem to want to “stick”. It will flow into the joint, but it does not provide any metal bonding. The internet provides a million options. It appears as if the solder and flux that I have are not appropriate for the application.

I am getting the heat to it ~350 -375F. The solder appears to flow and go to the heat, but it just does not want to stick or make bond.

Suggestions for both a Solder and a flux please, part numbers, pricing, where to get the supplies....

Thank you and regards,

Migrapefarmer

I soft soldered (2% silver bearing) stainless cheese knives that were 304 stainless. The wires were stainless as well and I used Sta-Kleen flux, heating it is the trick, any over heat or direct flame heat to the joint is a no no. Once stainless tarnishes the solder wont stick and the flux wont clean it off. Stainless is a bear to solder anyway and any discoloration of the base metal will result in problems thats a fact.

I would string the knives then flux the joints and solder with a large iron, making sure everything was clean and free of tarnish.

The sta kleen flux was what we used, I never found anything better in the 35 plus years of doing them. We bought the flux from a welding supplier.

Soft soldering cast iron I have no experience with.

I also have silver brazed (high temp) 440 stainless with good luck if indirect heat is used.